Unsold IPhones Piling Up at Leap Wireless

For one of the country's prepaid cellphone carriers, a big bet on the iPhone is becoming a big headache.

Leap Wireless International Inc., which operates the Cricket cellphone brand, said it is on pace to sell half as many iPhones as it committed to sell during the first year of its contract with Apple Inc., which ends in June.

As a result, Leap said, it could end up with $100 million worth of unsold iPhones by the middle of...